The interannual variability of cross-equatorial flows(CEFs)over the Asian–Australian monsoon(AAM)region during boreal summer was analyzed by applying the empirical orthogonal function(EOF)method to the meridional win...The interannual variability of cross-equatorial flows(CEFs)over the Asian–Australian monsoon(AAM)region during boreal summer was analyzed by applying the empirical orthogonal function(EOF)method to the meridional wind at 925 h Pa.The first mode(EOF1)exhibits an in-phase relationship among different CEF channels over the AAM region,which has received much attention owing to its tight linkage with ENSO.By contrast,the second mode(EOF2)possesses an out-of-phase relationship between the Bay of Bengal(BOB)CEF(90°E)and Australian CEF,among which the New Guinea CEF near 150°E shows the most significant opposite correlation with the BOB CEF.Observational and numerical model results suggest that the equatorially asymmetric heat source(sink)over the western(eastern)Maritime Continent,closely associated with the in-situ sea surface temperature anomaly,can induce cross-equatorial northerly(southerly)flow into the heating hemisphere,which dominates the out-of-phase relationship between the BOB and New Guinea CEFs.Furthermore,an equatorially symmetric heating over the central Pacific may indirectly change the CEFs by modulating the zonal atmospheric circulation near the Maritime Continent.展开更多
After being kept in captivity and isolated from natural predators for more than 1,200 years, P6re David＇s deer has been reintroduced in China and now occurs in a reserve where human activity is the only potential thr...After being kept in captivity and isolated from natural predators for more than 1,200 years, P6re David＇s deer has been reintroduced in China and now occurs in a reserve where human activity is the only potential threat. Antipredator vigilance i~ an important component of survival for many prey animals in their natural habitat. Do deer still adjust vigilance as a function of risk after such a long period of relaxed predation pressure？ Here, we examined vigilance levels in P6re David＇s deer groups as a function of group size, sex and level of human disturbance. The results showed that individual vigilance significantly decreased with group size in all-female groups but not in all-males or mixed-sex groups. In rutting season, males compete with one another and harass females, and we argue that vigilance is partly aimed at threatening males and that such vigilance increases with group size. This explains why overall vigilance did not vary with group size for males in general and for females in mixed-sex groups. Vigilance increased in more disturbed areas but in in male deer only. The results indicate that despite relaxed predation pressure over centuries, P6re David＇s deer can still adjust antipredator responses as a function of perceived risk. Such information may become useful in the rewilding programme now under way for this species in China [Current Zoology 59 （2）： 265-270, 2013].展开更多
基金jointly supported by the National Key Research and Development Program of China[grant number 2016YFA0600601]the National Natural Science Foundation of China[grant numbers 42030601 and 41875087]。
文摘The interannual variability of cross-equatorial flows(CEFs)over the Asian–Australian monsoon(AAM)region during boreal summer was analyzed by applying the empirical orthogonal function(EOF)method to the meridional wind at 925 h Pa.The first mode(EOF1)exhibits an in-phase relationship among different CEF channels over the AAM region,which has received much attention owing to its tight linkage with ENSO.By contrast,the second mode(EOF2)possesses an out-of-phase relationship between the Bay of Bengal(BOB)CEF(90°E)and Australian CEF,among which the New Guinea CEF near 150°E shows the most significant opposite correlation with the BOB CEF.Observational and numerical model results suggest that the equatorially asymmetric heat source(sink)over the western(eastern)Maritime Continent,closely associated with the in-situ sea surface temperature anomaly,can induce cross-equatorial northerly(southerly)flow into the heating hemisphere,which dominates the out-of-phase relationship between the BOB and New Guinea CEFs.Furthermore,an equatorially symmetric heating over the central Pacific may indirectly change the CEFs by modulating the zonal atmospheric circulation near the Maritime Continent.
基金Acknowledgements Financial support for this work was provided by the National Natural Science Foundation of China （No. 31000174 ＆ No. Jl103512）. We thank Prof. Ding Yuhua and other staff members at Dafeng Milu National Natural Reserve for supporting our field research in the reserve. We also thank Xianlong Li, Rongrong Wang, Jia He, Dameng Li, Ruonan Jia, Yilei Hua, and Long Wang for help with the field work, and Chen Ge and Cheng Huang for useful discussions.
文摘After being kept in captivity and isolated from natural predators for more than 1,200 years, P6re David＇s deer has been reintroduced in China and now occurs in a reserve where human activity is the only potential threat. Antipredator vigilance i~ an important component of survival for many prey animals in their natural habitat. Do deer still adjust vigilance as a function of risk after such a long period of relaxed predation pressure？ Here, we examined vigilance levels in P6re David＇s deer groups as a function of group size, sex and level of human disturbance. The results showed that individual vigilance significantly decreased with group size in all-female groups but not in all-males or mixed-sex groups. In rutting season, males compete with one another and harass females, and we argue that vigilance is partly aimed at threatening males and that such vigilance increases with group size. This explains why overall vigilance did not vary with group size for males in general and for females in mixed-sex groups. Vigilance increased in more disturbed areas but in in male deer only. The results indicate that despite relaxed predation pressure over centuries, P6re David＇s deer can still adjust antipredator responses as a function of perceived risk. Such information may become useful in the rewilding programme now under way for this species in China [Current Zoology 59 （2）： 265-270, 2013].
